Using paradigms like 10 dollars now, versus 11 dollars tomorrow, scientists found that the dorsolateral part of the prefrontal cortex, a region known to implement behavioral control, was crucial for making the choice to wait for higher but delayed payoffs.
Study leader Mathias Pessiglione said that however, these paradigms miss an essential feature of the inter-temporal conflicts we have to face in everyday life.
To reproduce this situation in the lab, the authors used more natural rewards like food items (for instance, a beer today or a bottle of champagne in a week from now).
Volunteers were confronted with choices between immediate rewards presented as pictures, and future rewards presented as text. In this case specifically, the ability to select future rewards was linked to the amount of hippocampus activity.
To complete the demonstration, individuals with hippocampus damage due to Alzheimer's disease were tested in the same choice task, as were individuals with a behavioral variant of frontotemporal dementia (bvFTD), arising from prefrontal degeneration.
Contrary to individuals with bvFTD, who exhibited excessive impulsivity in all sorts of choices, those with Alzheimer's disease were specifically biased towards immediate rewards when future rewards had to be imagined.